WASHINGTON – In our growing reliance on armed drones as instruments of war, how slippery is the slope we're sliding on? Imagine that Vladimir Putin began using drones to kill Ukrainians who opposed Russia's annexation of Crimea. If Putin claimed the targets were "members of anti-Russian terrorist groups," what credibility would the United States have to condemn such strikes?

This scenario is outlined in a chilling new report released Thursday by a bipartisan panel of military experts. The use of drones against al-Qaida and its affiliates, begun by the George W. Bush administration and greatly expanded by President Obama, risks becoming "a long-term killing program based on secret rationales," the report warns.

In the hypothetical Ukraine example, the world would demand proof that the individuals killed were indeed terrorists. The report notes that "Russia could simply repeat the words used by U.S. officials defending U.S. targeted killings, asserting that it could not provide any evidence without disclosing sources and methods."

The report was commissioned by the Stimson Center, a Washington think tank, and written by a panel that no one would consider a bunch of woolly-headed pacifists. Co-chairs of the group are retired Gen. John Abizaid, the former head of U.S. Central Command, and Rosa Brooks, a Georgetown University law professor. Included are former defense and intelligence officials from both Republican and Democratic administrations.

"We are concerned that the Obama administration's heavy reliance on targeted killings as a pillar of U.S. counterterrorism strategy rests on questionable assumptions, and risks increasing instability and escalating conflicts," the report concludes. "While tactical strikes may have helped keep the homeland free of major terrorist attacks, existing evidence indicates that both Sunni and Shiite Islamic extremist groups have grown in scope, lethality and influence."

In other words, we may be creating terrorists as quickly as we eliminate them. There is no indication, the report says, that drone strikes have "advanced long-term U.S. security interests."

The panel rejected the view, expressed by many critics, that drone strikes "cause disproportionate civilian casualties or turn killing into a 'video game.' " They do, however, enable U.S. policies that otherwise would be unlikely or impossible — especially "the cross-border use of lethal force against targeted individuals in an unprecedented and expanding way."

This ability to kill a specific person in a country with which the United States is not at war — such as Yemen, Somalia or Pakistan — raises strategic, legal and ethical questions, the report says.

One issue is the meaning of national sovereignty in the age of drone warfare. The United States says it has the right to conduct drone strikes against terrorists in countries whose governments are "unwilling or unable" to take action on their own. If the Obama administration has this right, does the Putin regime have it too? The Iranian government?

"The increasing use of lethal (drones) may create a slippery slope leading to continual or wider wars," the report says. Drones "may lower the bar to enter a conflict, without increasing the likelihood of a satisfactory outcome" — as may well happen, I would note, in the current Iraq crisis: It would be relatively easy to start blasting targets with missiles fired from drones, but to what end?

Meanwhile, since the United States has no monopoly on drone technology, other countries are likely to begin using the weapons in a similar way. It's hard for me to see this as an encouraging development.

The report criticizes the Obama administration for "the continuing lack of transparency relating to U.S. targeted killings." Even more troubling, perhaps, is that even if you assume U.S. officials are acting in good faith, "it would be difficult to conclude that U.S. targeted strikes are consistent with core rule-of-law norms."

Resentment of U.S. military power is hardly unprecedented. The real problem is that the Obama administration is establishing precedents for the use of drones that may come back to haunt us.

"Do as I say, not as I do" is fine when you're talking about aircraft carriers. But dozens of nations are mastering the use of drones. What will the world be like if everyone uses them the way we do?